Low frequency electromagnetic waves

Very Low Frequency (VLF) and Extremely Low Frequency (ELF) radio waves are used for communication between submarines, because higher-frequency radiation doesn't propagate well through sea water.

I think the main reason they're not used much outside of the water is simply that higher frequencies are easier to use for a number of reasons. For one thing, the lower the frequency you're trying to use, the longer your antenna needs to be. For another thing, the rate at which you can send information depends on the bandwidth (i.e., the range of frequencies you're using). There just isn't much bandwidth at the low-frequency end.